3 Pole MCB 20A-63A | AC Circuit Breaker

CNC 3 Pole MCB — Three-Phase Miniature Circuit Breaker

The CNC YCB7-63N 3 pole MCB is a three-phase miniature circuit breaker that protects three-phase circuits against overload and short circuit. It handles all three phase conductors (L1, L2, L3) simultaneously in a single trip mechanism, so a fault on any one phase disconnects all three — preventing the single-phasing condition that destroys three-phase motors and compressors.

Unlike the 4 Pole MCB, the 3P version does NOT switch the neutral — use it where neutral is handled separately by a busbar or where the load has no neutral (three-phase motors, delta-connected loads). For three-phase supplies that require neutral switching (3-phase main incomers, star-connected loads), choose the 4 Pole version instead.

Rated at 400V AC with C-curve trip response, this MCB is standard equipment in Pakistani commercial, industrial, and agricultural panels — from workshop machinery protection to submersible pump feeders. CNC Electric is a trusted MCB brand in Pakistan with a 5-year replacement warranty on all circuit breakers.

Specifications

Sizing a 3 Pole MCB for Motor Protection

For three-phase motor protection, pick a C-curve MCB rated at approximately 1.25× the motor full-load current. The table below shows typical sizing for Pakistani industrial motors at 400V 3-phase:

For heavy-inrush motors (star-delta starters, DOL starters on large pumps), consider a D-curve MCB variant, or combine this C-curve MCB with a dedicated motor-protection circuit breaker (MPCB) that senses motor-specific overload conditions. For loads above 63A, move to an MCCB breaker.

3 Pole vs 4 Pole — Which One Do You Need?

Typical Applications in Pakistan

Agricultural tube-wells and submersible pumps: 5-15 HP three-phase motors driven from WAPDA or generator-switched supplies. The 32A or 40A 3P MCB sits at the starter panel and protects the motor cable against overload and short circuit.

Workshop and light industrial machinery: lathes, milling machines, welding rectifiers, small compressors (delta-connected). Each machine gets its own 3P MCB feeder in the shop DB.

Three-phase air conditioning: larger commercial ACs (3 ton and above) are often fed from a 3P MCB when they use delta-connected compressors without neutral.

Commercial sub-distribution: when a three-phase sub-DB is fed by a common neutral busbar and only the three phases need to be switched at the feeder level.

Flour mills, cotton gins, food-processing plants: standard 3P MCB per motor bay, protecting the long cable run back to the main panel.

Why C-Curve for 3-Phase Motors

Three-phase motors draw a starting inrush of 5-7× full-load current for about 1-2 seconds during start-up (DOL start). A C-curve MCB (trips at 5-10× rated current after a short delay) tolerates this inrush without nuisance tripping while still protecting against sustained overload and short circuit.

For very heavy inrush — star-delta starters on 15 HP+ motors, or transformers — choose a D-curve variant (trips at 10-20× rated). For resistive-only loads (heaters), B-curve is adequate. For motor control in Pakistan, C-curve is the practical default.

Related Products

• Three-phase main incomer with neutral → 4 Pole MCB 20A-63A (Rs.1,900)
• Single-phase branch circuits → 1 Pole MCB 2A-63A (Rs.425)
• Single-phase main incomer → 2 Pole MCB 10A-63A (Rs.850)
• Above 63A or industrial fault levels → MCCB breakers 100A-1250A
• Three-phase generator switching → ATS 3-phase or 3P/4P changeover switch
• Motor contactor for start/stop → Magnetic contactors
• Motor soft-start control → Variable Frequency Drive (VFD)
• Three-phase voltage monitoring → Phase Sequence Relay
• Complete DB setup → DB boxes + breakers
• Read our guide → Types of Circuit Breakers in Pakistan

Frequently Asked Questions

What is a 3 Pole MCB?

A 3 Pole MCB is a miniature circuit breaker that protects three-phase circuits by disconnecting all three phase conductors (L1, L2, L3) together on overload or short circuit. The three poles are mechanically linked — a fault on any one phase trips all three. This prevents the dangerous single-phasing condition that destroys three-phase motors. The 3 Pole MCB does NOT switch the neutral wire; for circuits that need neutral switching, use a 4 Pole MCB instead.

What is the difference between 3 Pole and 4 Pole MCB?

A 3 Pole MCB switches only the three phase conductors (L1, L2, L3). A 4 Pole MCB switches all three phases plus the neutral. Use 3P where neutral is handled separately by a busbar, or where the load has no neutral (delta-connected motors). Use 4P for three-phase main incomers and for star-connected loads that need full isolation.

What size 3 Pole MCB for a 10 HP three-phase motor?

A 10 HP three-phase motor at 400V draws approximately 18-19A full-load current. Using the standard 1.25× sizing rule, a 32A C-curve 3 Pole MCB on 6mm² cable is the correct choice. The C-curve handles the DOL starting inrush of roughly 5-7× full-load current without nuisance tripping. Add a magnetic contactor for on/off control and thermal overload relay or MPCB for motor-specific overload protection.

What is the 3 Pole 63A MCB price in Pakistan?

The CNC YCB7-63N 3 Pole 63A MCB is available at Rs.1,350 at CNC Electric Pakistan. Competitor brands: Schneider iC60N 3P 63A typically costs Rs.5,500-7,000, and Chint NB1 3P 63A costs Rs.2,000-2,500. CNC offers equivalent IEC 60898 certified performance with 6kA breaking capacity at a significantly lower price with a 5-year replacement warranty included.

Can I use a 3 Pole MCB as main incomer on 3-phase WAPDA supply?

Only if the installation uses a common neutral busbar and the neutral is not routed through the main breaker. For a full-isolation 3-phase main incomer where both the three phases AND the neutral should disconnect together, use a 4 Pole MCB. In most modern installations a 4 Pole is the safer choice at the main incomer because it allows complete de-energisation of the DB during maintenance.

Does a 3 Pole MCB provide motor overload protection?

Partially. The 3 Pole MCB protects the motor cable and panel against short circuit, and it trips on sustained overload. However it does NOT detect motor-specific issues like stalled rotor, unbalanced phases, or thermal overload on only one phase. For complete motor protection, combine this 3P MCB with either (a) a thermal overload relay set to the motor FLC, or (b) a dedicated motor-protection circuit breaker (MPCB), or (c) a VFD that includes built-in motor protection.

What breaking capacity does the CNC 3 Pole MCB have?

6kA at 400V AC, per IEC 60898-1. This is adequate for residential, commercial, and small industrial panels where the prospective short-circuit current is under 6 kiloamperes (kA). For installations close to a large transformer where fault levels can exceed 6 kA, move up to an MCCB with 15-50 kA breaking capacity.

How wide is the 3 Pole MCB on the DIN rail?

The CNC YCB7-63N 3 Pole MCB is 54mm wide — three DIN-rail modules. Plan your DB box capacity accordingly. A 12-way DB box with three 3P MCBs already uses 9 of the 12 modules, leaving 3 modules for branch or auxiliary circuits.